I just touched down, kick the motherfucking field goal

“touchdown” meaning he’s now in the spot (back from jail) Or landing. In football When you score a touchdown you usually kick a field goal after wards.

This is one of the several Lil Wayne punchlines that make sense in passing, but under further analysis make little sense.
POINT AFTER TOUCHDOWN = 1 point (kicked after scoring 6 pts*)
FIELD GOAL = 3 points (kicked at any point during offensive possession)
He bent the rules of football to make his punchline work

Wayne could also be saying that you are not on his level since scoring a touch down in football takes more work than it does to kick a field goal.